MCBs

MCBs, or miniature circuit breakers, are a type of switch used to automatically turn off electrical circuits during abnormal conditions. MCBs often replace fuses in low voltage electrical circuits as they can be more reliable, much more sensitive and are resettable.


How an MCB Works


When continuous overcurrent flows through an MCB, a bimetallic strip is heated and causes it to bend. This bending of the bimetallic strip releases a mechanical latch opening the contacts and turning off the MCB, thereby stopping the current to flow in the circuit. To restart the flow of current the MCB must be manually turned on. This mechanism protects the MCB from faults arising due to overcurrent or overload and is intended to prevent the accidental overloading of the cable in a no-fault situation. The speed of the MCB tripping will vary with the degree of the overload. This is usually achieved by the use of a thermal device in the MCB. The second characteristic is the magnetic fault protection, which is intended to operate when the fault reaches a predetermined level and to trip the MCB within one-tenth of a second. The level of this magnetic trip gives the MCB its type characteristic.


MCBs are used to perform many functions such as local control switches, isolating switches against faults and overload protection devices for installation or specific equipment or appliances.


MCB Types


MCBs have three common types for circuit protection in residential, commercial and industrial applications. The use is classified by a type, which determines the tripping characteristics of the MCB:


Type B - trips between 3 and 5 times the load current


This type will trip instantly at a rate of three to five times its rated current. These are normally used for resistive or small inductive loads where switching surges are very small. Therefore, these are suitable for residential or light commercial installations.


Type C - trips between 5 and 10 times the full load current


This type will trip instantly at a rate of five to ten times its rated current. These are normally used for high inductive loads where switching surges are high such as small motors and fluorescent lighting. In such cases, type C MCBs are preferred to handle higher value of short circuit currents. Therefore, these are suitable for highly inductive commercial and industrial installations.


Type D - trips between 10 and 20 times the full load current


This type will trip instantly at a rate of ten to twenty-five times its rated current. These are normally used for very high inductive loads where high inrush current is very frequent. These are suitable for specific industrial and commercial applications. The common examples of such applications include x-ray machines, UPS systems, industrial welding equipment, large winding motors, etc.


How to select a suitable MCB for the application?


Focus on 3 main points to choose the right MCB for the electrical circuit


  1. Ampere rating

  2. Short circuit breaking capacity

  3. Application type

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Description Price Number of Poles Current Rating Model Number Range Series Rated AC Voltage Tripping Characteristics Mounting Style Rated DC Voltage Breaking Capacity at Maximum Voltage Rating Length Width Depth Break Time
RS庫存編號 772-1296
製造零件編號5SY4206-7
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TWD2,674.00
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2 6 A - Sentron 5SY4 400V Type C - - 10 kA 90mm 36mm 76mm -
RS庫存編號 622-0014
製造零件編號5SY4102-7
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TWD1,003.00
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1 2 A - Sentron 5SY4 230 V, 400V Type C - - 10 kA 89.8mm 17.6mm 76.4mm -
RS庫存編號 124-3156
製造零件編號5SY4150-7
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TWD1,940.00
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1 50 A - Sentron 5SY4 230 V, 400V Type C - - 10 kA 17.6mm 76.4mm 89.8mm -
RS庫存編號 772-1319
製造零件編號5SY4216-7
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TWD2,720.00
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2 16 A - Sentron 5SY4 400V Type C - - 10 kA 90mm 36mm 76mm -
RS庫存編號 521-4951
製造零件編號5SY6104-7
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TWD1,086.00
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1 4 A - Sentron 5SY6 230 V, 400V Type C - - 6 kA 89.8mm 17.6mm 76.4mm -
RS庫存編號 383-2024
製造零件編號5SY4110-7
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TWD1,041.00
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1 10 A - Sentron 5SY4 400V Type C - - 10 kA 89.8mm 17.6mm 76.4mm -
RS庫存編號 772-1372
製造零件編號5SY4310-7
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TWD3,633.00
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3 10 A - Sentron 5SY4 400V Type C - - 10 kA 89.8mm 52.8mm 76mm -
RS庫存編號 489-6669
製造零件編號5SY6316-6
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TWD2,425.00
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3 16 A - Sentron 5SY6 400V Type B - - 6 kA 89.8mm 52.8mm 76mm -
RS庫存編號 521-4939
製造零件編號5SY6102-7
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TWD977.00
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1 2 A - Sentron 5SY6 230 V, 400V Type C - - 6 kA 89.8mm 17.6mm 76.4mm -
RS庫存編號 772-1280
製造零件編號5SY4204-7
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TWD3,146.00
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2 4 A - Sentron 5SY4 400V Type C - - 10 kA 90mm 36mm 76mm -
RS庫存編號 772-1448
製造零件編號5SY4520-6
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TWD1,869.00
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- 20 A - Sentron 5SY4 230V Type B - - 10 kA 90mm 36mm 76mm -
RS庫存編號 489-6603
製造零件編號5SY6110-7
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TWD954.00
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1 10 A - Sentron 5SY6 230 V, 400V Type C - - 6 kA 89.8mm 17.6mm 76.4mm -
RS庫存編號 622-0070
製造零件編號5SY4301-7
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TWD4,689.00
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3 1 A - Sentron 5SY4 400V Type C - - 10 kA 89.8mm 52.8mm 76mm -
RS庫存編號 383-1958
製造零件編號5SY4106-6
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TWD567.00
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1 6 A - Sentron 5SY4 400V Type B - - 10 kA 89.8mm 17.6mm 76.4mm -
RS庫存編號 383-2096
製造零件編號5SY4325-6
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TWD3,078.00
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3 25 A - Sentron 5SY4 400V Type B - - 10 kA 89.8mm 52.8mm 76mm -
RS庫存編號 383-2018
製造零件編號5SY4106-7
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TWD641.00
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1 6 A - Sentron 5SY4 400V Type C - - 10 kA 89.8mm 17.6mm 76.4mm -
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TWD337.00
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1 16 A - Sentron 5SJ6 230 V, 400V Type B - 60V 6 kA 90mm 18mm 76mm -
RS庫存編號 199-5120
製造零件編號5SV6016-6KP13
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TWD6,413.00
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2 13 A 016-6KP13 SENTRON 5SV6 - Type B - - 1 A - - - -
RS庫存編號 202-7044
製造零件編號5SJ4104-7HG41
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1 4 A - SENTRON 5SJ4 - Type C - - 14 kA - - - -
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製造零件編號5SV6016-6KP16
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TWD6,172.00
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2 16 A 016-6KP16 SENTRON 5SV6 - Type B - - 1 A - - - -